JP6834986B2 - Method for manufacturing positive electrode active material precursor for non-aqueous electrolyte secondary battery, positive electrode active material for non-aqueous electrolyte secondary battery, positive electrode active material precursor for non-aqueous electrolyte secondary battery, positive electrode active material for non-aqueous electrolyte secondary battery Manufacturing method - Google Patents

Description

The present invention relates to a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery. The present invention relates to a method for producing a positive electrode active material for use.

In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, the development of small and lightweight non-aqueous electrolyte secondary batteries having a high energy density has been strongly desired. Further, it is strongly desired to develop a high output secondary battery as a large battery such as a power source for driving a motor.

As a secondary battery that meets these requirements, there is a lithium ion secondary battery. The lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as the negative electrode active material and the positive electrode active material.

Currently, research and development of lithium-ion secondary batteries is being actively carried out. Among them, a lithium ion secondary battery using a layered or spinel type lithium metal composite oxide as a positive electrode material is being put into practical use as a battery having a high energy density because a high voltage of 4V class can be obtained.

_{Currently, lithium cobalt composite oxide (LiCoO 2 ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO 2} ) using nickel, which is cheaper than cobalt, and lithium as the positive electrode material of the lithium ion secondary battery. Nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide using manganese (LiMn ₂ O ₄ ), lithium nickel manganese composite oxide (LiNi _0.5) Mn _0.5 O _2), lithium-rich nickel-cobalt-manganese composite oxide _{(Li 2 MnO 3 -LiNi x Mn} y Co z O 2) lithium composite oxide or the like is proposed.

Among these positive electrode active materials, a lithium excess nickel-cobalt-manganese composite oxide having a high capacity and excellent thermal stability has been attracting attention in recent years. This composite oxide is a layered compound like the lithium cobalt composite oxide and the lithium nickel composite oxide (see, for example, Non-Patent Document 1).

Then, for example, Patent Document 1 and Patent Document 2 disclose a method for producing a precursor for obtaining such a lithium excess nickel-cobalt-manganese composite oxide.

Japanese Patent Application Laid-Open No. 2011-0289999 Japanese Patent Application Laid-Open No. 2011-146392

"High Performance Lithium Ion Batteries: Solid Solution Positive Electrode Materials", FB Technical News, No. 66, January 2011, pp. 3-10

By the way, in order to aim at high output of a lithium ion secondary battery, it is effective to shorten the moving distance between the positive electrode and the negative electrode of lithium ion, so that the porous particles have uniform pores inside the particles. It is useful to use a positive electrode material containing.

However, although Patent Documents 1 and 2 disclose a method for producing a precursor, a composition of a positive electrode active material produced using the precursor, and the like, the structure of particles of the positive electrode active material is mentioned. In particular, the internal structure of the secondary particles has not been examined.

Therefore, in view of the above-mentioned problems of the prior art, in one aspect of the present invention, a positive electrode active material precursor for a non-aqueous electrolyte secondary battery capable of forming a positive electrode active material for a non-aqueous electrolyte secondary battery containing porous particles. The purpose is to provide.

According to one aspect of the present invention in order to solve the above problems.
Formula _{Ni x Co y Mn z M t} CO 3 ( where, in the formula, x + y + z + t = 1,0.05 ≦ x ≦ 0.3,0.1 ≦ y ≦ 0.4,0.55 ≦ z ≦ 0 8.8, 0 ≦ t ≦ 0.1 is satisfied, and M is one or more kinds of additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W). Represented nickel-cobalt-manganese carbonate complex and
It contains a functional group containing hydrogen and
Provided is a positive electrode active material precursor for a non-aqueous electrolyte secondary battery in which H / Me, which is a substance amount ratio of the contained hydrogen and the contained metal component Me, is 1.60 or more.

According to one aspect of the present invention, it is possible to provide a positive electrode active material precursor for a non-aqueous electrolyte secondary battery capable of forming a positive electrode active material for a non-aqueous electrolyte secondary battery containing porous particles.

FIG. 5 is a flow chart of a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention. SEM observation image of the precursor obtained in Example 1 according to the present invention. An SEM observation image of the positive electrode active material obtained in Example 1 according to the present invention. A partially enlarged view of FIG. 3A. The explanatory view of the cross-sectional structure of the coin-type battery produced in Example 1 which concerns on this invention. An SEM observation image of the positive electrode active material obtained in Comparative Example 2. A partially enlarged view of FIG. 5A.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments and does not deviate from the scope of the present invention. Can be modified and substituted in various ways.
[Positive electrode active material precursor for non-aqueous electrolyte secondary batteries]
In this embodiment, first, a configuration example of a positive electrode active material precursor for a non-aqueous electrolyte secondary battery will be described.

The positive electrode active material precursor for a non-aqueous electrolyte secondary battery of the present embodiment, the general formula _{Ni x Co y Mn z M t} CO 3 ( where, in the formula, x + y + z + t = 1,0.05 ≦ x ≦ 0.3 , 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, and M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, It can contain a nickel-cobalt-manganese carbonate complex represented by (one or more kinds of additive elements selected from Mo and W) and a functional group containing hydrogen.

Then, H / Me, which is the substance amount ratio of the contained hydrogen and the contained metal component Me, can be set to 1.60 or more.

As described above, the positive electrode active material precursor for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as “precursor”) is a nickel-cobalt-manganese carbonate complex and a functional group containing hydrogen. And can be included. The precursor can also be composed of a nickel cobalt manganese carbonate complex and a hydrogen-containing functional group.

The precursor of the present embodiment can include substantially spherical secondary particles formed by aggregating a plurality of fine primary particles, and can also be composed of the secondary particles.

The precursor of the present embodiment containing a nickel cobalt manganese carbonate composite and a functional group containing hydrogen is a crystal having high uniformity in particle size and fine crystals, and is a positive electrode for a non-aqueous electrolyte secondary battery. It can be used as a raw material for an active material, that is, as a precursor.

Hereinafter, the precursor of the present embodiment will be specifically described.
(composition)
Nickel-cobalt-manganese carbonate composite, as described above, the general _formula: is a _{Ni x Co y Mn z M t} CO nickel-cobalt-manganese composite basic carbonate salt form represented by _3.

However, in the above general formula, x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1. Filled, M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, W.

The precursors of the present embodiment include general formula 1: xMn ₂ (CO ₃ ) ₃ · yMn (OH) ₃ , general formula 2: xCo (CO ₃ ) ₂ · yCo (OH) ₂ · _{zH 2} O, and General formula 3: Ni ₄ CO ₃ (OH) ₆ (H ₂ O) _{4 and the} like can contain a compound having an indefinite composition mixed with carbonates and hydroxides, and the above-mentioned states are summarized. It is expressed by a general formula.

When the precursor of the present embodiment is used as a precursor of the positive electrode active material of a non-aqueous electrolyte secondary battery, a nickel cobalt manganese carbonate composite is used in order to further improve battery characteristics such as cycle characteristics and output characteristics. It is also possible to add one or more kinds of additive elements to the above-mentioned.

One or more kinds of additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W are uniformly inside the secondary particles within a predetermined atomic number ratio t. It is preferable that the distribution and / or the surface of the secondary particles is uniformly covered.

However, in the nickel-cobalt-manganese carbonate composite, if the atomic number ratio t of the added element exceeds 0.1, the metal element contributing to the redox reaction (Redox reaction) decreases, and the battery capacity may decrease. ..

Further, even when the nickel-cobalt-manganese carbonate composite does not contain an additive element, the positive electrode active material produced by using the precursor of the present embodiment has sufficient battery characteristics such as cycle characteristics and output characteristics. It has characteristics. Therefore, it is not necessary to contain an additive element.

Therefore, it is preferable to adjust the additive element so that the atomic number ratio is within the range of 0 ≦ t ≦ 0.1.

As the additive element, one or more selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W can be used as described above, and molybdenum is particularly used as the additive element. It is preferable to include it. That is, above the general _{formula: Ni x Co y Mn z M} t CO 3 added element M in the preferably contains a Mo. According to the study by the inventors of the present invention, when the additive element contains molybdenum, the initial discharge capacity is determined in a non-aqueous electrolyte secondary battery using a positive electrode active material prepared using the precursor. This is because it can be increased in particular.

Further, the nickel cobalt manganese carbonate composite contains 0.5 at% or more and 5 at% or less of molybdenum among the metal components in the nickel cobalt manganese carbonate composite, that is, Ni, Co, Mn, and the additive element M. Is more preferable. This is because the above-mentioned effect of increasing the initial discharge capacity can be particularly exhibited by setting the content of molybdenum in the metal component of the nickel-cobalt-manganese carbonate composite to 0.5 at% or more. Further, molybdenum has an effect of accelerating sintering during firing, but when the content of molybdenum in the metal component of the nickel cobalt manganese carbonate composite is 5 at% or less, an excessively large crystal is formed. This is preferable because it is possible to prevent an increase in resistance and a decrease in discharge capacity in a battery manufactured by using the precursor.

Further, according to the study by the inventors of the present invention, it was confirmed that the inclusion of molybdenum as the additive element has the effect of reducing the specific surface area of the positive electrode active material produced by using the precursor. This is because the addition of molybdenum structurally changes the fine pores in the positive electrode active material into large pores. Further, according to the study by the inventors of the present invention, by controlling the specific surface area of the positive electrode active material in ^{the range of 1.5 m 2} / g or more and 15.0 m ² / g or less, the positive electrode mixture paste can be produced. Can be facilitated. Therefore, from the viewpoint of controlling the specific surface area within the above range, it is preferable that the additive element contains molybdenum.

It is preferable that the additive element is uniformly distributed inside the secondary particles contained in the precursor (hereinafter, also simply referred to as “precursor particles”) and / or the surface of the secondary particles is uniformly coated.

In the nickel-cobalt-manganese carbonate composite, the state of the additive element is not particularly limited. However, it is preferable that the additive element is uniformly distributed inside the nickel-cobalt-manganese carbonate composite and / or uniformly coated on the surface as described above. This is because the additive element is distributed (coated) inside and / or on the surface of the nickel-cobalt-manganese carbonate composite, so that the battery characteristics can be improved when the precursor of the present embodiment is used as the precursor of the positive electrode active material. This is because it can be particularly improved.

In the nickel cobalt manganese carbonate composite, even when the amount of one or more additive elements added is particularly small, the carbonate composite is more than inside the carbonate composite in order to sufficiently enhance the effect of improving the battery characteristics. It is preferable to increase the concentration of one or more additive elements on the surface.

As described above, in the nickel cobalt manganese carbonate composite, even if the amount of one or more additive elements added is small, the effect of improving the battery characteristics can be obtained and the decrease in battery capacity can be suppressed. it can.

In addition, the precursor of the present embodiment can contain the above-mentioned hydrogen-containing functional groups. Examples of the hydrogen-containing functional group include a hydrogen group and a hydroxyl group. The hydrogen-containing functional group is mixed in the manufacturing process, and H / Me, which is the substance amount ratio of the hydrogen H contained in the precursor of the present embodiment and the contained metal component Me, is 1.60 or more. Therefore, when the positive electrode active material is used, the particles can be made porous, which is preferable.

The metal component Me contained in the precursor here includes Ni, Co, Mn and M which is an additive element mentioned in the above general formula.

Further, the precursor of the present embodiment may contain a nickel cobalt manganese carbonate complex and a component other than a functional group containing hydrogen, but contains a nickel cobalt manganese carbonate complex and hydrogen. It can also be composed of functional groups. Even when the precursor of the present embodiment is composed of a nickel-cobalt-manganese carbonate complex and a hydrogen-containing group, it does not exclude the inclusion of unavoidable components in the manufacturing process or the like. Absent.
[Manufacturing method of positive electrode active material precursor for non-aqueous electrolyte secondary battery]
Next, a configuration example of a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as “precursor production method”) will be described.

Since the precursor described above can be produced by the method for producing a precursor of the present embodiment, some of the contents already described will be omitted.

In the method for producing a precursor of the present embodiment, a precursor can be obtained by a crystallization reaction, and the obtained precursor can be washed and dried if necessary.

Specifically, the method for manufacturing a precursor of the present embodiment, the general formula _{Ni x Co y Mn z M t} CO 3 ( where, in the formula, x + y + z + t = 1,0.05 ≦ x ≦ 0.3,0 .1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, where M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, A positive electrode active material precursor for a non-aqueous electrolyte secondary battery containing a nickel-cobalt-manganese carbonate complex represented by (1 or more kinds of additive elements selected from W) and a functional group containing hydrogen. Can have the following steps with respect to the manufacturing method of.

An initial aqueous solution containing an alkaline substance and / or an ammonium ion feeder in the presence of carbonate ions, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component. And, a nucleation generation step to generate nuclei in a mixed aqueous solution.
A particle growth process that grows the nuclei formed in the nucleation process.
Then, the nucleation step can be carried out in an oxygen-containing atmosphere by controlling the pH value of the mixed aqueous solution to 7.5 or less based on the reaction temperature of 40 ° C.

A configuration example of the flow of the method for producing the precursor of the present embodiment shown in FIG. 1 will be described below. As shown in FIG. 1, in the method for producing a precursor of the present embodiment, (A) a nucleation step and a nucleation step are performed, and then particles of the precursor are generated by a coprecipitation method (B) particle growth. Has a process.

In the conventional continuous crystallization method, the nucleation reaction and the particle growth reaction proceed simultaneously in the same reaction vessel, so that the particle size distribution of the obtained compound particles is wide.

On the other hand, in the method for producing a precursor of the present embodiment, the time when the nucleation reaction mainly occurs (nucleation step) and the time when the particle growth reaction mainly occurs (particle growth step) are clearly separated. .. As a result, even if both steps are performed in the same reaction vessel, precursor particles having a narrow particle size distribution can be obtained. In addition, a nuclear crushing step in which the addition of the raw material is stopped and only stirring is performed can be included between the two steps.

Hereinafter, each step of the method for producing a precursor of the present embodiment will be specifically described.
(1) Nucleation Step The nucleation step will be described with reference to FIG.

As shown in FIG. 1, in the nucleation step, first, an ion-exchanged water (water) can be mixed with an alkaline substance and / or an ammonium ion feeder in a reaction vessel to prepare an initial aqueous solution.

The ammonium ion feeder is not particularly limited, but is preferably one or more selected from an aqueous ammonium carbonate solution, an aqueous ammonia solution, an aqueous ammonium chloride solution, and an aqueous ammonium sulfate solution.

Further, the alkaline substance is not particularly limited, but it is preferably one or more selected from sodium carbonate, sodium hydrogen carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

In the nucleation step, it is preferable to maintain the pH value of the mixed aqueous solution obtained by adding an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component to the initial aqueous solution at a lower pH value than in the particle growth step described later. By keeping the pH value of the mixed aqueous solution low, the number of nuclei in the mixed aqueous solution can be reduced and the number can be increased, and the particle size of the secondary particles contained in the obtained precursor can be reduced. Because it becomes.

Therefore, it is preferable to add an acidic substance to the initial aqueous solution to adjust the pH value to 5.4 or more and 7.5 or less, and more preferably to 6.4 or more and 7.4 or less. .. In particular, it is more preferable to adjust the pH value to 6.4 or more and 7.0 or less.

During the nucleation step, the pH value of the mixed aqueous solution is also preferably in the above range. Since the pH value of the mixed aqueous solution fluctuates slightly during the nucleation step, the maximum pH value of the mixed aqueous solution during the nucleation step can be used as the pH value of the mixed aqueous solution in the nucleation step. It is preferable that the pH value of the mixed aqueous solution is in the above range.

The acidic substance is not particularly limited, and for example, sulfuric acid or the like can be preferably used. As the acidic substance, it is preferable to use the same type of acid as the metal salt used when preparing the aqueous solution containing the metal component to be added to the initial aqueous solution.

During the nucleation step, the pH value of the mixed aqueous solution is preferably controlled within 0.2 above and below the center value (set pH value).

In the nuclear formation step, the atmosphere is controlled by blowing an oxygen-containing gas into the reaction vessel in which the initial aqueous solution is prepared, and then an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component described later is flowed at a constant flow rate, for example. The pH value of the mixed aqueous solution can be controlled to be within a predetermined range. As a result, it reacts with dissolved oxygen contained in the mixed aqueous solution and oxygen contained in the oxygen-containing gas supplied to the reaction vessel to generate irregular fine particles of carbonate which are not single crystals. Further, by injecting an oxygen-containing gas, it is possible to easily mix a functional group containing hydrogen with the precursor as compared with the case of an inert gas atmosphere, and the hydrogen contained in the obtained precursor and the hydrogen contained in the precursor can be easily mixed. The H / Me, which is the ratio of the amount of substance to the contained metal component Me, can be 1.60 or more.

In the nucleation step, oxygen-containing gas can be continuously supplied into the reaction vessel even while an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component is added to the initial aqueous solution.

When the oxygen-containing gas is supplied into the reaction vessel, the amount of the oxygen-containing gas supplied can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. Since the dissolved oxygen in the mixed aqueous solution is consumed during the nucleation step, if the amount of dissolved oxygen in the mixed aqueous solution is more than half of the saturated amount, it means that sufficient dissolved oxygen / oxygen can be supplied for the reaction.

As the oxygen-containing gas, for example, air or the like can be used.

In the nuclear formation step, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component are added to and mixed with the initial aqueous solution in the reaction vessel. An aqueous solution can be formed.

When an aqueous solution containing nickel as a metal component is added to the initial aqueous solution, the pH value of the obtained mixed aqueous solution is preferably controlled to 7.5 or less based on the reaction temperature of 40 ° C. It is more preferably controlled to 4 or less, and further preferably to 7.0 or less. Therefore, it is preferable that the aqueous solution containing a metal component such as an aqueous solution containing nickel is not added all at once, but is gradually added dropwise to the initial aqueous solution.

Further, in order to control the pH of the mixed aqueous solution, the pH-adjusted aqueous solution can be added dropwise as well as the aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component. The pH adjusting aqueous solution at this time is not particularly limited, and for example, an aqueous solution containing an alkaline substance and / or an ammonium ion feeder can be used. The alkaline substance and the ammonium ion feeder are not particularly limited, but the same substances as those described in the initial aqueous solution can be used. The method of supplying the pH-adjusted aqueous solution into the reaction vessel is not particularly limited. For example, a pump capable of controlling the flow rate of the obtained mixed aqueous solution while sufficiently stirring the mixed aqueous solution, such as a metering pump, is used to prepare the mixed aqueous solution. It may be added so that the pH value is maintained in a predetermined range.

Then, as described above, particles that become the core of the precursor can be generated in the mixed aqueous solution obtained by adding an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component to the initial aqueous solution. .. Whether or not a predetermined amount of nuclei are generated in the mixed aqueous solution can be determined by the amount of the metal salt contained in the mixed aqueous solution.

Here, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component, which are added to the initial aqueous solution in the nucleation step, will be described.

An aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component can contain a metal compound containing each metal component. That is, for example, an aqueous solution containing cobalt as a metal component can contain a metal compound containing cobalt.

As the metal compound, it is preferable to use a water-soluble metal compound, and examples of the water-soluble metal compound include nitrates, sulfates, hydrochlorides and the like. Specifically, for example, nickel sulfate, cobalt sulfate, manganese sulfate and the like can be preferably used.

The aqueous solution containing nickel as a metal component, the aqueous solution containing cobalt as a metal component, and the aqueous solution containing manganese as a metal component are partially or wholly mixed in advance, and a mixed aqueous solution containing a metal component is used. Can be added to the initial aqueous solution.

The composition ratio of each metal in the obtained precursor is the same as the composition ratio of each metal in the mixed aqueous solution containing a metal component. Therefore, for example, a metal to be dissolved so that the composition ratio of each metal contained in the mixed aqueous solution containing a metal component added to the initial aqueous solution in the nuclear formation step is equal to the composition ratio of each metal in the precursor to be produced. It is preferable to adjust the ratio of the compound to prepare a mixed aqueous solution containing a metal component.

When a specific metal compound reacts with each other to generate an unnecessary compound by mixing a plurality of metal compounds, an aqueous solution containing each metal component is simultaneously made into an initial aqueous solution at a predetermined ratio. It may be added.

When the aqueous solution containing each metal component is not mixed and is added individually to the initial aqueous solution, the composition ratio of each metal contained in the entire aqueous solution containing the metal component to be added is the composition of each metal in the generated precursor. It is preferable to prepare an aqueous solution containing each metal component so as to be equal to the ratio.

As described above, the precursor produced by a production method of a precursor of the present embodiment, the general formula _{Ni x Co y Mn z M t} CO 3 ( where, in the formula, x + y + z + t = 1,0.05 ≦ x ≤0.3, 0.1≤y≤0.4, 0.55≤z≤0.8, 0≤t≤0.1, where M is Mg, Ca, Al, Ti, V, Cr, It can contain a nickel-cobalt-manganese carbonate complex represented by (one or more kinds of additive elements selected from Zr, Nb, Mo, and W) and a functional group containing hydrogen.

That is, in addition to nickel, cobalt, and manganese, additive elements can be further contained.

Therefore, in the nucleation step, one or more kinds of additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W (hereinafter, also simply referred to as "additive elements") are used as needed. An aqueous solution containing (described) (hereinafter, also simply referred to as “aqueous solution containing additive elements”) can also be added to the initial aqueous solution. Since it is preferable that the additive element contains Mo as described above, it is preferable to use an aqueous solution containing at least molybdenum as a metal component as the aqueous solution containing the additive element.

When an aqueous solution containing nickel as a metal component is mixed to prepare a metal component-containing mixed aqueous solution and then added to the initial aqueous solution, the aqueous solution containing an additive element is added and mixed with the metal component-containing mixed aqueous solution. You can leave it.

Further, when an aqueous solution containing nickel as a metal component or the like is individually added to the initial aqueous solution without being mixed, the aqueous solution containing the additive element can be individually added to the initial aqueous solution.

Here, the aqueous solution containing the additive element can be prepared by using, for example, a compound containing the additive element. Examples of the compound containing the additive element include titanium sulfate, ammonium peroxotitanate, potassium titanium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, potassium chromate, zirconium sulfate, zirconium nitrate, niobium oxalate, and molybdenum. Examples thereof include ammonium acid, sodium tungstate, ammonium tungstate, and the like, and the compound can be selected according to the element to be added.

As described above, it is preferable that the additive element is uniformly distributed inside the nuclear particles contained in the precursor and / or the surface of the nuclear particles is uniformly coated.

Then, by adding the aqueous solution containing the above-mentioned additive element to the mixed aqueous solution, the additive element can be uniformly dispersed inside the nuclear particles contained in the precursor.

Further, in order to uniformly coat the surface of the secondary particles of the precursor with the additive element, for example, after the completion of the particle growth step described later, a coating step of coating with the additive element can be carried out. The coating step will be described later in the particle growth step.

Further, in the nucleation step, in the presence of carbonate ions, an aqueous solution containing nickel as a metal component or the like is added to and mixed with the initial aqueous solution to obtain a mixed aqueous solution, and nucleation can be generated in the mixed aqueous solution. At this time, the method for supplying carbonate ions is not particularly limited, and for example, carbon dioxide ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with the oxygen-containing gas described later into the reaction vessel. In addition, carbonate ions can be supplied by using a carbonate when preparing an initial aqueous solution or a pH-adjusted aqueous solution.

As described above, in the nucleation step, in the presence of carbonate ions, an aqueous solution containing nickel as a metal component or the like is added to and mixed with the initial aqueous solution to obtain a mixed aqueous solution, and nucleation is generated in the mixed aqueous solution. it can.

At this time, the concentration of the metal compound in the mixed aqueous solution is preferably 1 mol / L or more and 2.6 mol / L or less, and more preferably 1.5 mol / L or more and 2.2 mol / L or less.

This is because if the concentration of the metal compound in the mixed aqueous solution is less than 1 mol / L, the amount of crystallized substances per reaction vessel is small, which is not preferable because the productivity is lowered. On the other hand, if the concentration of the metal compound in the mixed aqueous solution exceeds 2.6 mol / L, the saturation concentration at room temperature may be exceeded, and crystals may reprecipitate and clog the equipment piping. is there.

The concentration of the metal compound refers to an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, an aqueous solution containing manganese as a metal component, and, in some cases, further added addition to the mixed aqueous solution. It means the concentration of a metal compound derived from an aqueous solution containing an element.

In the nucleation step, the temperature of the mixed aqueous solution is preferably maintained at 20 ° C. or higher, more preferably 30 ° C. or higher. The upper limit of the temperature of the mixed aqueous solution in the nucleation step is not particularly limited, but is preferably 70 ° C. or lower, more preferably 50 ° C. or lower, for example.

This is because, in the nucleation step, when the temperature of the mixed aqueous solution is less than 20 ° C., the solubility is low, so that nucleation is likely to occur and control may be difficult.

On the other hand, in the nucleation step, if the temperature of the mixed aqueous solution exceeds 70 ° C., the primary crystal may be distorted and the tap density may be lowered.

In the nucleation step, the concentration of ammonium ions in the mixed aqueous solution is not particularly limited, but is preferably 0 g / L or more and 20 g / L or less, and particularly preferably kept at a constant value.

The pH value in the mixed aqueous solution, other ammonium ion concentration, the amount of dissolved oxygen, and the like can be measured by a general pH meter, ion meter, and dissolved oxygen meter, respectively.

After the nucleation step is completed, that is, after the addition of the metal component-containing mixed aqueous solution to the initial aqueous solution is completed, it is preferable to continue stirring the mixed aqueous solution to crush the generated nuclei (nucleation crushing). Process). When the nuclear crushing step is carried out, the time is preferably 1 minute or more, and more preferably 3 minutes or more. By carrying out the nuclear crushing step, it is possible to more reliably suppress the agglomeration of the generated nuclei, the coarsening of the particle size, and the decrease in the density inside the particles.
(2) Particle Growth Step Next, the particle growth step will be described with reference to FIG.

In the particle growth step, the nuclei generated in the nucleation step can be grown.

Specifically, for example, as shown in FIG. 1, in the particle growth step, the pH value of the mixed aqueous solution obtained in the nucleation step can be adjusted first.

At this time, the pH value of the mixed aqueous solution can be adjusted to be 6.0 or more and 9.0 or less based on, for example, a reaction temperature of 40 ° C. At this time, the pH value of the mixed aqueous solution is more preferably adjusted to be 6.4 or more and 8.0 or less, and further preferably adjusted to be 7.1 or more and 8.0 or less. The pH at this time can be adjusted, for example, by adding a pH adjusting solution described later.

This is because by setting the pH value of the mixed aqueous solution to 6.0 or more and 9.0 or less, it is possible to suppress the residual impurity cations.

In the particle growth step, the mixed aqueous solution after the nucleation formation step contains an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions. And can be added and mixed.

The mixed aqueous solution after the nucleation step here is preferably a mixed aqueous solution whose pH is adjusted after the nucleation step as described above.

Further, the aqueous solution containing nickel as a metal component, the aqueous solution containing cobalt as a metal component, and the aqueous solution containing manganese as a metal component are partially or wholly mixed as in the case of the nucleation step. , May be added to the mixed aqueous solution as a mixed aqueous solution containing a metal component. In addition, when a plurality of metal compounds are mixed and specific metal compounds react with each other to generate an unnecessary compound, an aqueous solution containing each metal component is individually added to the mixed aqueous solution. May be good.

Further, when an aqueous solution containing nickel as a metal component is added to the mixed aqueous solution, an aqueous solution containing an additive element can be added at the same time as in the case of the nucleation step. As described above, an aqueous solution containing an additive element can be mixed with a mixed aqueous solution containing a metal component and added. Further, when the aqueous solution containing each metal component is individually added to the mixed aqueous solution, the aqueous solution containing the additive element can also be individually added to the mixed aqueous solution.

As the aqueous solution containing nickel as a metal component, the aqueous solution containing cobalt as a metal component, and the aqueous solution containing manganese as a metal component, the same aqueous solution as in the case of the nucleation step can be used. Further, the concentration and the like may be adjusted separately.

When an aqueous solution containing nickel as a metal component is added to the mixed aqueous solution, the pH value of the obtained mixed aqueous solution is preferably controlled within a predetermined range as described later. Therefore, an aqueous solution or the like containing nickel as a metal component can be gradually added dropwise to the mixed aqueous solution instead of being added all at once. Therefore, a solution containing these metal components, a mixed aqueous solution containing the metal component, or the like can be supplied to the reaction vessel at a constant flow rate, for example.

In the particle growth step, an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component can be added to the mixed aqueous solution after adjusting the pH value as described above. In this case as well, for the same reason that the pH value was adjusted before the start of the particle growth step, the pH value of the mixed aqueous solution was in the same range as that of the mixed aqueous solution after adjusting the pH value, that is, 6.0 or more and 9.0. It is preferably maintained below, more preferably 6.4 or more and 8.0 or less, and even more preferably 7.1 or more and 8.0 or less.

In the particle growth step, by controlling the pH value of the mixed aqueous solution within the above range, a precursor having a small amount of impurities remaining can be obtained.

Since the pH value of the mixed aqueous solution fluctuates slightly during the particle growth step, the maximum pH value of the mixed aqueous solution during the particle growth step can be used as the pH value of the mixed aqueous solution in the particle growth step. It is preferable that the pH value of the mixed aqueous solution is in the above range.

In particular, during the particle growth step, it is preferable to control the fluctuation range of the pH value of the mixed aqueous solution to be within 0.2 above and below the center value (set pH value). This is because when the fluctuation range of the pH value of the mixed aqueous solution is large, the growth of the particles contained in the precursor is not constant, and uniform particles having a narrow particle size distribution range may not be obtained. ..

When supplying an aqueous solution containing a metal component or a mixed aqueous solution containing a mixed metal component as described above, it is preferable to add a pH adjusting aqueous solution at the same time so that the pH of the mixed aqueous solution can be maintained within a predetermined range. As the pH-adjusted aqueous solution, the same pH-adjusted aqueous solution as in the nuclear production step can be used, and the pH-adjusted aqueous solution at this time is not particularly limited, but for example, an aqueous solution containing an alkaline substance and / or an ammonium ion feeder can be used. Can be used. The alkaline substance and the ammonium ion feeder are not particularly limited, but the same substances as those described in the initial aqueous solution can be used. The method of supplying the pH-adjusted aqueous solution into the reaction vessel is not particularly limited. For example, a pump capable of controlling the flow rate of the obtained mixed aqueous solution while sufficiently stirring the mixed aqueous solution, such as a metering pump, is used to prepare the mixed aqueous solution. It may be added so that the pH value is maintained in a predetermined range.

In the particle growth step, the ammonium ion concentration in the mixed aqueous solution is preferably 0 g / L or more and 20 g / L or less, and particularly preferably kept at a constant value.

This is because the nuclei of the precursor particles can be uniformly grown by setting the concentration of ammonium ions to 20 g / L or less. In addition, since the ammonium ion concentration is maintained at a constant value in the particle growth step, the solubility of metal ions can be stabilized and the particle growth of uniform precursor particles can be promoted.

The lower limit of the ammonium ion concentration can be appropriately adjusted as needed, and is not particularly limited. Therefore, the ammonium ion concentration in the mixed aqueous solution is adjusted to be 0 g / L or more and 20 g / L or less by, for example, using an ammonium ion feeder in the initial aqueous solution or the pH adjusting aqueous solution and adjusting the supply amount thereof. It is preferable to do so.

Further, in the particle growth step, an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component can be added and mixed with the mixed aqueous solution in the presence of carbonate ions. At this time, the method for supplying carbonate ions is not particularly limited, and for example, carbon dioxide ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with the oxygen-containing gas described later into the reaction vessel. Further, when preparing the above-mentioned initial aqueous solution or pH-adjusted aqueous solution, carbonate ions can be used to supply carbonate ions.

In the particle growth step, an oxygen-containing gas is blown into the reaction vessel to control the atmosphere so as to create an oxygen-containing atmosphere, and an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component is flowed at a constant flow rate, for example. Can be supplied at. As a result, it reacts with dissolved oxygen contained in the mixed aqueous solution and oxygen contained in the oxygen-containing gas supplied to the reaction vessel, and irregularly shaped fine particles that are not single crystals of carbonate are further aggregated. It is possible to generate large secondary particles. Further, by injecting an oxygen-containing gas, it is possible to make it easier to mix a functional group containing hydrogen with the precursor as compared with the case of an inert gas atmosphere, and the hydrogen contained in the obtained precursor and the hydrogen contained in the precursor can be easily mixed. The H / Me, which is the ratio of the amount of substance to the contained metal component Me, can be 1.60 or more.

When oxygen-containing gas is supplied into the reaction vessel in the particle growth step, the supply amount of the oxygen-containing gas can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. Since the dissolved oxygen in the mixed aqueous solution is consumed during the particle growth step, if the amount of dissolved oxygen in the mixed aqueous solution is more than half of the saturated amount, it means that sufficient dissolved oxygen / oxygen can be supplied for the reaction.

As the oxygen-containing gas, for example, air or the like can be used.

The particle size of the secondary particles contained in the precursor can be controlled by the reaction time of the particle growth step.

That is, in the particle growth step, if the reaction is continued until the particles grow to a desired particle size, a precursor having secondary particles having a desired particle size can be obtained.

Then, after obtaining the precursor in the particle growth step, it is also possible to further have a coating step of coating the surface of the particles of the obtained precursor with an additive element as described above. That is, the method for producing a precursor of the present embodiment may further include a coating step of coating the precursor particles (secondary particles) obtained in the particle growth step with an additive element.

The coating step can be, for example, any of the following steps.

For example, first, an aqueous solution containing an additive element is added to a slurry in which the precursor particles are suspended, and the additive element is precipitated on the surface of the precursor particles by a crystallization reaction.

As for the slurry in which the precursor particles are suspended, it is preferable to make the precursor particles into a slurry by using an aqueous solution containing an additive element. Further, when the aqueous solution containing the additive element is added to the slurry in which the precursor particles are suspended, the pH of the mixed aqueous solution of the slurry and the aqueous solution containing the additive element is 6.0 or more and 9.0 or less. It is preferable to control. This is because the surface of the precursor particles can be particularly uniformly coated with the additive element by controlling the pH of the mixed aqueous solution of the slurry and the aqueous solution containing the additive element within the above range.

Further, the coating step may be a step of spraying an aqueous solution containing an additive element or a slurry on the precursor particles to dry them.

In addition, the coating step may be a step of spray-drying a slurry in which precursor particles and a compound containing an additive element are suspended.

Further, the step of mixing the precursor particles and the compound containing the additive element by the solid phase method can also be used.

As the aqueous solution containing the additive element described here, the same aqueous solution as that described in the nucleation step can be used. Further, in the coating step, an alkoxide solution containing the additive element may be used instead of the aqueous solution containing the additive element.

When an aqueous solution containing an additive element is added to an initial aqueous solution or a mixed aqueous solution in a nucleation generation step or a particle growth step as described above, and a coating step is performed to coat the surface of the precursor particles with the additive element. It is preferable to reduce the amount of additive element ions added to the initial aqueous solution or the mixed aqueous solution in the nucleation formation step or the particle growth step by the amount to be coated. By reducing the amount of the aqueous solution containing the additive element to be added to the mixed aqueous solution by the amount to be coated, the atomic number ratio of the additive element contained in the obtained precursor to other metal components is desired. This is because it can be the value of.

As described above, the coating step of coating the surface of the precursor particles with the additive element may be performed on the precursor particles after the particle growth step is completed and the particles are heated.

In the method for producing a precursor of the present embodiment, it is preferable to use an apparatus in which the precursor which is a product is not recovered until the reaction in the nucleation step to the particle growth step is completed. Examples of such an apparatus include a commonly used batch reaction vessel in which a stirrer is installed. By adopting such a device, unlike a continuous crystallizer that recovers products by overflow, there is no problem that growing particles are recovered at the same time as the overflow liquid, so that the particle size distribution is narrow. It is preferable because particles having a uniform particle size can be obtained.

Further, in order to control the atmosphere of the reaction vessel, it is preferable to use a device capable of controlling the atmosphere, such as a closed device.

By using an apparatus capable of controlling the atmosphere of the reaction vessel, the particles containing the precursor can have the structure as described above, and the coprecipitation reaction can proceed almost uniformly. It is possible to obtain particles having an excellent distribution, that is, particles having a narrow range of particle size distribution.

In the particle growth step, the pH value of the mixed aqueous solution obtained in the nucleation step is adjusted to be within a predetermined range, and an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component is further added to the mixed aqueous solution. By doing so, uniform precursor particles can be obtained.

By carrying out the above particle growth step, an aqueous precursor particle solution, which is a slurry containing the precursor particles, can be obtained. Then, after the particle growth step is completed, the washing step and the drying step can be carried out.
(3) Cleaning Step In the cleaning step, the slurry containing the precursor particles obtained in the above-mentioned particle growth step can be washed.

In the washing step, the slurry containing the precursor particles can be first filtered, washed with water, and filtered again.

Filtration may be performed by a commonly used method, and for example, a centrifuge or a suction filter is used.

Further, the washing with water may be carried out by a method usually used, and it is sufficient that excess raw materials and the like contained in the particles of the precursor can be removed.

As the water used for washing with water, it is preferable to use water having as little impurity content as possible, and more preferably pure water, in order to prevent contamination with impurities.
(4) Drying Step In the drying step, the particles of the precursor washed in the washing step can be dried.
First, in the drying step, for example, the washed precursor particles can be dried by setting the drying temperature to 80 ° C. or higher and 230 ° C. or lower.

After the drying step, the precursor can be obtained.

According to the method for producing a precursor of the present embodiment, a precursor capable of forming a positive electrode active material for a non-aqueous electrolyte secondary battery containing porous particles can be obtained.

Further, according to the method for producing a precursor of the present embodiment, the time when the nuclear formation reaction mainly occurs (nuclear generation step) and the time when the particle growth reaction mainly occurs (particle growth step) are clearly separated. Even if both steps are carried out in the same reaction vessel, precursor particles (secondary particles) having a narrow particle size distribution can be obtained.

In addition, in the method for producing a precursor of the present embodiment, the crystal size of the precursor particles obtained during the crystallization reaction can be controlled.

Therefore, according to the method for producing a precursor of the present embodiment, it is possible to obtain a precursor having a small particle size of the primary particles, high particle size uniformity of the secondary particles, and a high density (tap density). it can.

Further, in the method for producing a precursor of the present embodiment, the nucleation step and the particle growth step can be separated in one reaction vessel only by mainly adjusting the pH of the reaction solution. Therefore, since the method for producing the precursor of the present embodiment is easy and suitable for large-scale production, it can be said that its industrial value is extremely large.
[Positive electrode active material for non-aqueous electrolyte secondary batteries]
Next, a configuration example of a positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as “positive electrode active material”) will be described.

The positive electrode active material of the present embodiment relates to a positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium metal composite oxide.
Then, lithium metal composite oxide is represented by the general formula _{Li 1 + α Ni x Co y} Mn z M t O 2 (0.25 ≦ α ≦ 0.55, x + y + z + t = 1,0.05 ≦ x ≦ 0.3,0. 1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, M is an additive element, and Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo , One or more elements selected from W).

The positive electrode active material of the present embodiment contains porous secondary particles in which a plurality of primary particles are aggregated, the porosity inside the secondary particles is 10% or more and 30% or less, and the number ratio of the secondary particles is set. It can be 80% or more.

The positive electrode active material of the present embodiment is _{a lithium metal composite oxide in which two types of layered compounds represented by Li 2} M1O ₃ and _{Li M2O 2} are dissolved, and more specifically, a lithium excess nickel cobalt manganese composite oxide. Can include. The positive electrode active material of the present embodiment can also be composed of the above lithium metal composite oxide.

In the above formula, M1 is a metal element containing at least Mn adjusted to have an average of tetravalent, and M2 is a metal element containing at least Ni, Co, and Mn adjusted to have an average of trivalent. is there.

Then, it is assumed that the composition ratio of Ni, Co, and Mn shown in the above-mentioned precursor is M1 + M2. Further, since _{the abundance ratio of Li 2} M1O ₃ and _{Li M2O 2} is excessive lithium, it is assumed _{that Li 2 M1O 3} is not 0%.

As described above, in the precursor as well, in order to further improve the battery characteristics such as the cycle characteristics and output characteristics of the positive electrode active material of the non-aqueous electrolyte secondary battery, the lithium metal composite oxide is made of Mg, as described above. It can contain one or more additive elements selected from Ca, Al, Ti, V, Cr, Zr, Nb, Mo and W. The content of the additive element is preferably adjusted so that the atomic number ratio t is within the range of 0 ≦ t ≦ 0.1 for the reason described above in the precursor.

As the additive element, one or more selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W can be used as described above, and the additive element particularly contains molybdenum. Is preferable. That is, above the general _{formula: Li 1 + α Ni x Co} y Mn z M t additive element M O ₂ preferably contains a Mo. This is because, according to the study by the inventors of the present invention, when the positive electrode active material contains molybdenum as an additive element, the initial discharge capacity can be particularly increased in the battery using the positive electrode active material. Is.

Further, the lithium metal composite oxide has a molybdenum content of 0.5 at% or more and 5 at% or less among the metal components other than Li in the lithium metal composite oxide, that is, Ni, Co, Mn, and the additive element M. More preferably. This is because the above-mentioned effect of increasing the initial discharge capacity can be particularly exhibited by setting the content of molybdenum in the metal component excluding Li in the lithium metal composite oxide to 0.5 at% or more. Further, molybdenum has an effect of accelerating sintering during firing, but by setting the content of molybdenum in the metal component excluding Li in the lithium metal composite oxide to 5 at% or less, an excessively large crystal is generated. This is preferable because it can prevent this from occurring and reliably prevent an increase in resistance and a decrease in discharge capacity in a battery manufactured by using the precursor.

Further, according to the study by the inventors of the present invention, it was confirmed that the inclusion of molybdenum as the additive element has the effect of reducing the specific surface area of the positive electrode active material produced by using the precursor. This is because the addition of molybdenum structurally changes the fine pores in the positive electrode active material into large pores. Further, according to the study by the inventors of the present invention, by controlling the specific surface area of the positive electrode active material in ^{the range of 1.5 m 2} / g or more and 15.0 m ² / g or less, the positive electrode mixture paste can be produced. It can be facilitated and the output characteristics can be improved. Therefore, from the viewpoint of controlling the specific surface area within the above range, it is preferable that the additive element contains molybdenum.

The positive electrode active material of the present embodiment has a structure having uniform pores up to the center of the contained secondary particles, and the reaction surface area can be increased by adopting such a porous structure. .. Further, since the electrolytic solution infiltrates through the grain boundaries or pores between the primary particles in the outer shell and lithium is inserted and removed at the reaction interface inside the particles, the movement of Li ions and electrons is not hindered. The output characteristics can be improved.

The positive electrode active material of the present embodiment preferably has a porosity of 10% or more and 30% or less inside the secondary particles contained therein. Further, it is preferable that 80% or more of the porous secondary particles having pores up to the central portion are contained in proportion to the number of the particles. The porosity of the porous secondary particles can be calculated by, for example, observing the cross-sectional structure of the positive electrode active material with SEM and performing image processing or the like. In addition, the ratio of the number of porous secondary particles was determined by observing the cross-sectional structure of a plurality of, for example, 100 secondary particles of the positive electrode active material by SEM, among which the secondary particles having pores to the center. It can be calculated by counting the ratio.

Since the positive electrode active material of the present embodiment has a porous structure, its specific surface area can be increased. The specific surface area of the positive electrode active material of the present embodiment can be arbitrarily selected depending on the characteristics required for the positive electrode active material and is not particularly limited, but may be, for example, 1.5 m ² / g or more. preferable. This is because by setting the specific surface area of the positive electrode active material of the present embodiment to 1.5 m ² / g or more, the production of the positive electrode mixture paste can be facilitated and the output characteristics can be improved. Is.

The upper limit of the specific surface area of the positive electrode active material of the present embodiment is not particularly limited ^{, but is preferably 15.0 m 2} / g or less, and more preferably 13.0 m ² / g or less, for example.

However, when it is required to particularly increase the reaction surface area and the output characteristics, the specific surface area of the positive electrode active material of the present embodiment shall be 5.0 m ² / g or more and 15.0 m ² / g or less. Is preferable. Further, when it is particularly required to particularly facilitate the production of the positive electrode mixture paste, the specific surface area of the positive electrode active material of the present embodiment is 1.5 m ² / g or more and 8.0 m ² / g or less. Is preferable.

Further, according to the positive electrode active material of the present embodiment, the porous structure can enhance the output characteristics in the case of a battery and also increase the tap density.

The tap density of the positive electrode active material of the present embodiment is not particularly limited, but is preferably 1.7 g / cc or more, and more preferably 1.8 g / cc or more.

The positive electrode active material of the present embodiment preferably has a high initial discharge capacity of 250 mAh / g or more when used for the positive electrode of a 2032 type coin-type battery, for example. Further, it is preferable that the discharge capacity under the high discharge rate condition (2C) is 195 mAh / g or more.

The discharge capacity under the high discharge rate condition (2C) can be measured a plurality of times, for example, three times at 2C, and can be used as an average value of the plurality of measurements.
[Manufacturing method of positive electrode active material for non-aqueous electrolyte secondary batteries]
Next, a configuration example of a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as a “method for producing a positive electrode active material”) will be described.

The method for producing the positive electrode active material of the present embodiment is not particularly limited as long as the positive electrode active material can be produced so as to have the particle structure of the positive electrode active material described above, but if the following method is adopted, the positive electrode is said. It is preferable because the active material can be produced more reliably.

The method for producing the positive electrode active material of the present embodiment can have the following steps.

A heat treatment step of heat-treating the positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained by the method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery described above at a temperature of 80 ° C. or higher and 600 ° C. or lower.
A mixing step of adding and mixing a lithium compound to the particles obtained by the heat treatment step to form a lithium mixture.
A firing step in which a lithium mixture is fired at a temperature of 600 ° C. or higher and 1000 ° C. or lower in an oxidizing atmosphere.

Hereinafter, each step will be described.
(1) Heat Treatment Step In the heat treatment step, the precursor described above can be heat-treated at a temperature of 80 ° C. or higher and 600 ° C. or lower. By performing the heat treatment, the water content contained in the precursor can be removed, and it is possible to prevent the number of metal atoms and the ratio of lithium atoms in the finally obtained positive electrode active material from fluctuating.

It is not necessary to convert all the precursors to nickel-cobalt-manganese composite oxides as long as the water content can be removed to the extent that the number of metal atoms and the ratio of lithium atoms in the positive electrode active material do not vary. However, in order to further reduce the variation, it is preferable to convert all the precursor particles into composite oxide particles at a heating temperature of 500 ° C. or higher.

In the heat treatment step, the heat treatment temperature is set to 80 ° C. or higher because if the heat treatment temperature is less than 80 ° C., excess water in the particles of the precursor cannot be removed and the above variation cannot be suppressed. is there.

On the other hand, the heat treatment temperature is set to 600 ° C. or lower because if the heat treatment temperature exceeds 600 ° C., the particles may be sintered by roasting and composite oxide particles having a uniform particle size may not be obtained. ..

The above variation can be suppressed by determining the metal component contained in the particles of the precursor corresponding to the heat treatment conditions in advance by analysis and determining the ratio with the lithium compound.

The heat treatment atmosphere is not particularly limited and may be a non-reducing atmosphere, but it is preferably performed in an air stream that can be easily performed.

The heat treatment time is not particularly limited, but if it is less than 1 hour, the excess water of the precursor particles may not be sufficiently removed. Therefore, at least 1 hour or more is preferable, and 2 hours or more and 15 hours or less is more preferable. preferable.

The equipment used for the heat treatment is not particularly limited, as long as the precursor particles can be heated in a non-reducing atmosphere, preferably in an air stream, such as an electric furnace that does not generate gas. It is preferably used.
(2) Mixing Step The mixing step is a step of adding and mixing a lithium compound to the heat-treated particles obtained by heating in the heat treatment step to form a lithium mixture.

The heat-treated particles obtained by heat treatment in the heat treatment step include nickel cobalt manganese carbonate composite particles and / or nickel cobalt manganese composite oxide particles.

The heat-treated particles and the lithium compound are the sum of the atomic numbers of metals other than lithium in the lithium mixture, that is, the sum of the atomic numbers of nickel, cobalt, manganese and additive elements (Me), and the atomic number of lithium (Li). It is preferable to mix so that the ratio (Li / Me) is 1.1 or more and 1.8 or less. At this time, it is more preferable to mix so that Li / Me is 1.3 or more and 1.5 or less.

That is, since Li / Me does not change before and after the firing step, the Li / Me mixed in this mixing step becomes Li / Me in the positive electrode active material, so that the Li / Me in the lithium mixture is the positive electrode active material to be obtained. It is mixed so as to be the same as Li / Me in.

The lithium compound used to form the lithium mixture is not particularly limited, but one or more selected from, for example, lithium hydroxide, lithium nitrate, and lithium carbonate is preferable because it is easily available. Can be used.

In particular, in consideration of ease of handling and stability of quality, it is more preferable to use one or more selected from lithium hydroxide and lithium carbonate as the lithium compound used when forming the lithium mixture.

A general mixer can be used for mixing, and for example, a shaker mixer, a lady gem mixer, a julia mixer, a V blender, or the like may be used.
(3) Firing step The firing step is a step of calcining the lithium mixture obtained in the above mixing step to obtain a positive electrode active material. When the mixed powder is fired in the firing step, lithium in the lithium compound diffuses into the heat-treated particles, so that a lithium nickel cobalt manganese composite oxide is formed.

The firing temperature of the lithium mixture at this time is not particularly limited, but is preferably 600 ° C. or higher and 1000 ° C. or lower, for example.

This is because by setting the firing temperature to 600 ° C. or higher, the diffusion of lithium into the heat-treated particles is sufficiently promoted, the residual lithium and unreacted particles are suppressed, and when used in a battery. This is because sufficient battery characteristics can be obtained.

However, if the firing temperature exceeds 1000 ° C., the composite oxide particles may be violently sintered and abnormal grain growth may occur, and the particles after firing become coarse and have fine pores inside the particles. This is because there is a possibility that Since such a positive electrode active material has a reduced specific surface area, when used in a battery, there arises a problem that the resistance of the positive electrode increases and the battery capacity decreases.

Since the firing temperature of the lithium mixture also affects the specific surface area of the obtained positive electrode active material, it can be selected from the above-mentioned temperature ranges according to the specific surface area required for the positive electrode active material. For example, when it is required to particularly suppress the specific surface area of the positive electrode active material, it is preferable to set the firing temperature to a higher temperature, for example, 900 ° C. or higher and 950 ° C. or lower. According to the study of the inventor of the present invention, the specific surface area of the obtained positive electrode active material can be set to 1.5 m ² / g or more and 8.0 m ² / g or less by firing in such a temperature range, and the positive electrode can be obtained. The production of the mixture paste can be particularly facilitated. Further, when the positive electrode active material is used as a non-aqueous electrolyte secondary battery, the battery capacity can be kept high, which is preferable.

From the viewpoint of uniformly reacting the heat-treated particles with the lithium compound, it is preferable to raise the temperature to the above temperature by setting the heating rate to 3 ° C./min or more and 10 ° C./min or less.

Furthermore, the reaction can be made more uniform by holding the lithium compound at a temperature near the melting point for about 1 hour or more and 5 hours or less. When the temperature is maintained near the melting point of the lithium compound, the temperature can be raised to a predetermined firing temperature thereafter.

Of the firing times, the holding time at the firing temperature is preferably 1 hour or more, and more preferably 2 hours or more and 24 hours or less.

This is because the formation of the lithium nickel-cobalt-manganese composite oxide can be sufficiently promoted by holding the calcination temperature for 2 hours or more.

After the holding time at the firing temperature is completed, the rate of descent is not particularly limited, but when the lithium mixture is loaded in a sack and fired, the descent rate is set to 2 ° C./min or more and 10 in order to suppress deterioration of the sack. It is preferable to cool the atmosphere to 200 ° C. or lower at ° C./min or lower.

The atmosphere at the time of firing is preferably an oxidizing atmosphere, more preferably an atmosphere having an oxygen concentration of 18% by volume or more and 100% by volume or less, and a mixed atmosphere of oxygen and an inert gas having the oxygen concentration. Is particularly preferable. That is, firing is preferably performed in the atmosphere or an oxygen-containing gas.

As described above, it is preferable to create an atmosphere having an oxygen concentration of 18% by volume or more, because the crystallinity of the lithium nickel-cobalt-manganese composite oxide can be sufficiently enhanced by setting the oxygen concentration to 18% by volume or more. Because it can be done.

In particular, considering the battery characteristics, it is preferable to perform the operation in an oxygen stream.

The furnace used for firing is not particularly limited as long as it can heat the lithium mixture in the atmosphere or an oxygen-containing gas, but from the viewpoint of keeping the atmosphere in the furnace uniform, gas generation is generated. No electric furnace is preferred. Further, either a batch type or a continuous type furnace can be used.

When lithium hydroxide or lithium carbonate is used as the lithium compound, it is preferable to perform calcining after the mixing step and before the firing step. The calcining temperature is preferably lower than the firing temperature and preferably 350 ° C. or higher and 800 ° C. or lower, and more preferably 450 ° C. or higher and 780 ° C. or lower.

The calcination time is preferably about 1 hour or more and 10 hours or less, and more preferably 3 hours or more and 6 hours or less.

It is preferable that the calcining is carried out at the calcining temperature. In particular, it is preferable to perform calcining at the reaction temperature of lithium hydroxide or lithium carbonate and the heat-treated particles.

When calcining is performed, lithium is sufficiently diffused into the heat-treated particles, and a uniform lithium nickel-cobalt-manganese composite oxide can be obtained, which is preferable.

The particles of the lithium nickel cobalt manganese composite oxide obtained by the firing step may be aggregated or slightly sintered.

In this case, it may be crushed. Thereby, the positive electrode active material of the present embodiment containing the lithium nickel cobalt manganese composite oxide can be obtained.

In addition, crushing means that mechanical energy is applied to an agglomerate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and the secondary particles themselves are hardly destroyed. It is an operation to separate secondary particles and loosen agglomerates.
[Non-aqueous electrolyte secondary battery]
Next, a configuration example of the non-aqueous electrolyte secondary battery of the present embodiment will be described. The non-aqueous electrolyte secondary battery of the present embodiment can have a positive electrode using the positive electrode active material described above.

First, the structure of the non-aqueous electrolyte secondary battery of the present embodiment will be described.

The non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as “secondary battery”) is a general non-aqueous electrolyte secondary battery except that the above-mentioned positive electrode active material is used as the positive electrode material. It can have a structure substantially similar to that of the above.

The secondary battery of the present embodiment can have, for example, a case and a structure including a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator housed in the case.

More specifically, the secondary battery of the present embodiment can have an electrode body in which a positive electrode and a negative electrode are laminated via a separator. Then, the electrode body is impregnated with a non-aqueous electrolyte to collect current between the positive electrode current collector of the positive electrode and the positive electrode terminal communicating with the outside, and between the negative electrode current collector of the negative electrode and the negative electrode terminal communicating with the outside. It can be connected using a lead or the like to form a structure sealed in a case.

Needless to say, the structure of the secondary battery of the present embodiment is not limited to the above example, and various shapes such as a tubular shape and a laminated shape can be adopted as the outer shape thereof.

(Positive electrode)
First, the positive electrode, which is a feature of the secondary battery of the present embodiment, will be described. The positive electrode is a sheet-shaped member, and is formed by applying and drying a positive electrode mixture paste containing the above-mentioned positive electrode active material on the surface of a current collector made of aluminum foil, for example.

The positive electrode is appropriately processed according to the battery used. For example, a cutting process for forming an appropriate size according to a target battery, a pressure compression process using a roll press or the like for increasing the electrode density, and the like are performed.

The positive electrode mixture paste can be formed by adding a solvent to the positive electrode mixture and kneading it. The positive electrode mixture can be formed by mixing the above-mentioned positive electrode active material in powder form with a conductive material and a binder.

The conductive material is added in order to give appropriate conductivity to the electrode. The conductive material is not particularly limited, and for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.) or a carbon black material such as acetylene black or ketjen black can be used.

The binder serves to hold the positive electrode active material particles together. The binder used in this positive electrode mixture is not particularly limited, and for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, cellulose-based resin, etc. Polyacrylic acid or the like can be used.

Activated carbon or the like may be added to the positive electrode mixture, and the electric double layer capacity of the positive electrode can be increased by adding activated carbon or the like.

The solvent dissolves the binder and disperses the positive electrode active material, the conductive material, activated carbon, and the like in the binder. The solvent is not particularly limited, but for example, an organic solvent such as N-methyl-2-pyrrolidone can be used.

Further, the mixing ratio of each substance in the positive electrode mixture paste is not particularly limited. For example, when the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass or more and 95 parts by mass or less, and the conductivity is similar to that of the positive electrode of a general non-aqueous electrolyte secondary battery. The content of the material can be 1 part by mass or more and 20 parts by mass or less, and the content of the binder can be 1 part by mass or more and 20 parts by mass or less.

(Negative electrode)
The negative electrode is a sheet-like member formed by applying a negative electrode mixture paste to the surface of a metal leaf current collector such as copper and drying it. Although the components constituting the negative electrode mixture paste, their composition, the material of the current collector, and the like are different, the negative electrode is formed by a method substantially the same as that of the positive electrode, and is subjected to various treatments as necessary like the positive electrode. Is done.

The negative electrode mixture paste is made into a paste by adding an appropriate solvent to a negative electrode mixture in which a negative electrode active material and a binder are mixed.

As the negative electrode active material, for example, a substance containing lithium such as metallic lithium or a lithium alloy, or a storage substance capable of storing and desorbing lithium ions can be adopted.

The occlusal substance is not particularly limited, and for example, a calcined product of an organic compound such as natural graphite, artificial graphite, or phenol resin, and a powdered material of a carbon substance such as coke can be used. When such an occlusion material is adopted as the negative electrode active material, a fluororesin such as PVDF can be used as the binder as in the case of the positive electrode, and the solvent for dispersing the negative electrode active material in the binder can be used. An organic solvent such as N-methyl-2-pyrrolidone can be used.

(Separator)
The separator is arranged so as to be sandwiched between the positive electrode and the negative electrode, and has a function of separating the positive electrode and the negative electrode and holding an electrolyte. As the separator, for example, a thin film such as polyethylene or polypropylene, which has a large number of fine pores, can be used, but is not particularly limited as long as it has the above function.

(Non-aqueous electrolyte)
The non-aqueous electrolyte is a solution of a lithium salt as a supporting salt in an organic solvent.

Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate; and chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate; further, tetrahydrofuran and 2-. Ether compounds such as methyl tetrahydrofuran and dimethoxyethane; sulfur compounds such as ethylmethylsulfone and butane sulton; phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc., alone or in admixture of two or more. , Can be used.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and a composite salt thereof can be used.

The non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, or the like in order to improve the battery characteristics.

(Characteristics of non-aqueous electrolyte secondary battery of this embodiment)
The non-aqueous electrolyte secondary battery of the present embodiment can have, for example, the above configuration and has a positive electrode using the positive electrode active material described above, so that a high initial discharge capacity and a low positive electrode resistance can be obtained. High capacity and high output.

(Use of the secondary battery of this embodiment)
Since the secondary battery of the present embodiment has the above-mentioned properties, it is suitable as a power source for small portable electronic devices (notebook personal computers, mobile phone terminals, etc.) that always require high capacity.

Further, the secondary battery of the present embodiment is also suitable for a battery as a power source for driving a motor, which requires high output. As the size of the battery increases, it becomes difficult to ensure the safety, and an expensive protection circuit is indispensable. However, the secondary battery of the present embodiment has excellent safety, so that the safety is ensured. Not only is it easier to do, but it also simplifies expensive protection circuits and makes them cheaper. Further, since it is possible to reduce the size and increase the output, it is suitable as a power source for transportation equipment whose mounting space is restricted.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.

The sample preparation conditions and evaluation results in each Example and Comparative Example will be described below.
[Example 1]
1. 1. Preparation and evaluation of precursors First, precursors were prepared by the following procedure.

Throughout all the examples and comparative examples, unless otherwise specified, each sample of Wako Pure Chemical Industries, Ltd.'s reagent special grade is used for producing the precursor, the positive electrode active material, and the secondary battery.
(Nucleation process)
(1) Preparation of initial aqueous solution First, put water up to about 1.2 L in the reaction vessel (5 L) and set the temperature in the vessel to 40 ° C. while stirring, and then perform the following nucleation step and nucleation. The temperature of the mixed aqueous solution was controlled to 40 ° C. in the crushing step and the particle growth step. The temperature of the initial aqueous solution and the mixed aqueous solution was controlled by adjusting the temperature of the warming water for the reaction tank provided around the reaction tank.

Then, an appropriate amount of 25% by mass aqueous ammonia was added to the water in the reaction vessel to adjust the ammonium ion concentration in the initial aqueous solution to 5 g / L.

The pH was adjusted to 6.4 by further adding 64% sulfuric acid to the initial aqueous solution.

Then, as an oxygen-containing gas, air gas was supplied into the reaction vessel at 4 L / min from an air compressor, and the inside of the vessel was purged to create an atmosphere containing oxygen. The supply of air gas is continued until the particle growth step is completed, and the inside of the reaction vessel is maintained in an air atmosphere, that is, an oxygen-containing atmosphere.
(2) Preparation of Metal Component-Containing Mixed Aqueous Solution Next, nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water to prepare a metal component-containing mixed aqueous solution having a metal ion concentration of 2.0 mol / L. In this mixed aqueous solution containing metal components, the element molar ratio of each metal was adjusted to be Ni: Co: Mn = 0.165: 0.165: 0.67.
(3) Adjustment of pH-adjusted aqueous solution Sodium carbonate and ammonium carbonate were dissolved in water to prepare a pH-adjusted aqueous solution having a carbonate ion concentration of 2.2 mol / L. In addition, sodium carbonate and ammonium carbonate in the pH-adjusted aqueous solution were added so as to have a molar ratio of 9: 2.
(4) Addition of a mixed aqueous solution containing a metal component to the initial aqueous solution, and adding the mixed aqueous solution containing a mixed metal component to the initial aqueous solution in the reaction vessel at 10.3 ml / min. Was added to prepare a mixed aqueous solution.

When the mixed aqueous solution containing a metal component is added, a pH adjusting aqueous solution is added at the same time to control the pH value of the mixed aqueous solution in the reaction vessel so as not to exceed 6.4 (nucleation pH value). The nucleation step was carried out by crystallizing for a minute. Further, during the nucleation step, the fluctuation range of the pH value of the mixed aqueous solution was within the range of 0.2 above and below the center value (set pH value) 6.2.
(5) Nuclear crushing step After that, stirring was continued for 5 minutes to crush the nucleus.
(Particle growth process)
In the particle growth step, the same metal component-containing mixed aqueous solution and pH-adjusted aqueous solution as in the nucleation step were used. The experimental procedure of the particle growth process will be described below.
(1) Adjustment of pH of mixed aqueous solution In the particle growth step, a pH-adjusted aqueous solution was first added to the mixed aqueous solution obtained in the nucleation step to set the pH value to 7.4 (based on a liquid temperature of 40 ° C.).
(2) Addition of metal component-containing mixed aqueous solution to mixed aqueous solution, mixing 10.3 ml / min of metal component-containing mixed aqueous solution to the mixed aqueous solution after adjusting the pH value. Was added at the ratio of.

At this time, the addition amounts of the mixed aqueous solution containing a metal component and the pH adjusting aqueous solution were controlled so that the pH value of the mixed aqueous solution did not exceed 7.4 based on the reaction temperature of 40 ° C.

After continuing this state for 100 minutes, stirring was stopped and crystallization was completed.

Then, the product obtained by the particle growth step was washed with water, filtered, and dried to obtain precursor particles (washing and drying steps).

In the particle growth step, the pH value is controlled by adjusting the supply flow rate of the pH-adjusted aqueous solution with a pH controller, and the fluctuation range of the pH value of the mixed aqueous solution is 0 above and below the center value (set pH value) 7.2. It was within the range of .2.

Further, in the nucleation step and the particle growth step, the ammonium ion concentration in the mixed aqueous solution was maintained at 5 g / L.

(Evaluation of precursor)
The obtained precursor was dissolved with an inorganic acid and then chemically analyzed by ICP emission spectroscopy. As a result, the composition thereof was Ni: Co: Mn = 14.9 at%: 16.7 at%: 68.4 at%. It was confirmed that it was a carbonate composed of. Furthermore, the elemental amount of hydrogen (H) was measured using an elemental analyzer (Thermo Fisher Scientific model: FlashEA 1112), and the substance amount ratio with the metal (Ni + Co + Mn) was calculated to be as high as 1.69. It was confirmed that it contained hydrogen. It was also confirmed that it has a functional group containing hydrogen.

Further, the particles of the precursor, the average particle diameter D _50, a laser diffraction scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac HRA) result of measurement with a mean particle size is 7.4μm I was able to confirm that.

Next, SEM (scanning electron microscope S-4700, manufactured by Hitachi High-Technologies Co., Ltd.) of the obtained precursor particles was observed (magnification: 3000 times), and the obtained precursor particles were omitted. It was confirmed that it was spherical and the particle size was almost uniform. In the case of such a shape, the spherical property of the precursor particles shown in Table 2 is judged to be 〇.

The SEM observation results are shown in FIG.
2. 2. Production and evaluation of positive electrode active material Next, the positive electrode active material was produced and evaluated using the obtained precursor.

(Manufacturing of positive electrode active material)
The precursor was heat-treated at 500 ° C. for 2 hours in an air (oxygen: 21% by volume) air stream to convert it into composite oxide particles which were heat-treated particles and recovered.

Next, the heat-treated particles and a lithium compound were mixed to obtain a lithium mixture.

Specifically, lithium carbonate was weighed so that Li / Me = 1.5 of the obtained lithium mixture, and mixed with the heat-treated particles to prepare a lithium mixture.

Mixing was performed using a shaker mixer device (TURBULA Type T2C, manufactured by Willie et Bacoffen (WAB)).

The obtained lithium mixture was calcined in the air (oxygen: 21% by volume) at 500 ° C. for 5 hours, then calcined at 800 ° C. for 2 hours, cooled, and then crushed to obtain a positive electrode active material. ..

The composition of the obtained positive electrode active material is represented by _{Li 1.5} Ni _0.149 Co _0.167 Mn _0.684 O _2.

(Evaluation of positive electrode active material)
When the particle size distribution of the obtained positive electrode active material was measured by the same method as in the case of the precursor particles, it was confirmed that the average particle size was 7.0 μm.

In addition, cross-sectional SEM observation of the positive electrode active material was performed.

In observing the cross section of the positive electrode active material by SEM, secondary particles of a plurality of positive electrode active material particles were embedded in the resin, and the cross section of the particles could be observed by cross-section polisher processing, and then the observation was performed by SEM. ..

3A and 3B show the cross-sectional SEM observation results of the positive electrode active material. FIG. 3B is a partially enlarged view of FIG. 3A, which is an enlarged view of the particles surrounded by the dotted line in FIG. 3A.

As shown in FIGS. 3A and 3B, it was confirmed that the obtained positive electrode active material was substantially spherical. In this case, the sphericalness is evaluated as 〇 in Table 3. In addition, it was confirmed that the structure had uniform pores up to the center inside the secondary particles.

Further, as a result of observing 100 or more particles of these cross-sectional SEM images, the ratio of the number of particles having pores to the center (porous particles) was 100%. Moreover, when the porosity of the secondary particles was measured using image analysis software, it was 22%.

Furthermore, when the tap density was measured, it was confirmed that the tap density was 1.8 g / cc.

The tap density was measured after filling a 20 ml graduated cylinder with the obtained positive electrode active material and then densely filling the graduated cylinder with a method of repeating free fall from a height of 2 cm 500 times.

Further, when the specific surface area of the obtained positive electrode active material was determined by a flow method gas adsorption method specific surface area measuring device (Multisorb, manufactured by Yuasa Ionics Co., Ltd.), it was confirmed that it was ^{12.4 m 2 / g.}

[Manufacturing of secondary batteries]
A 2032 type coin-type battery was prepared and evaluated using the obtained positive electrode active material.

The configuration of the manufactured coin-type battery will be described with reference to FIG. FIG. 4 schematically shows a cross-sectional configuration diagram of a coin-type battery.

As shown in FIG. 4, the coin-type battery 10 is composed of a case 11 and an electrode 12 housed in the case 11.

The case 11 has a positive electrode can 111 that is hollow and has one end opened, and a negative electrode can 112 that is arranged in the opening of the positive electrode can 111. When the negative electrode can 112 is arranged in the opening of the positive electrode can 111, , A space for accommodating the electrode 12 is formed between the negative electrode can 112 and the positive electrode can 111.

The electrode 12 is composed of a positive electrode 121, a separator 122, and a negative electrode 123, and is laminated so as to be arranged in this order so that the positive electrode 121 contacts the inner surface of the positive electrode can 111 and the negative electrode 123 contacts the inner surface of the negative electrode can 112. Is housed in the case 11.

The case 11 is provided with a gasket 113, and the gasket 113 is fixed between the positive electrode can 111 and the negative electrode can 112 so as to maintain an electrically insulated state. Further, the gasket 113 also has a function of sealing the gap between the positive electrode can 111 and the negative electrode can 112 to hermetically and liquidally shut off the inside and the outside of the case 11.

The coin-type battery 10 was manufactured as follows. First, 52.5 mg of the obtained positive electrode active material, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed together with a solvent (N-methyl-2-pyrrolidone), and the diameter was 11 mm at a pressure of 100 MPa. A positive electrode 121 was produced by press molding to a thickness of 100 μm. The prepared positive electrode 121 was dried at 120 ° C. for 12 hours in a vacuum dryer. Using the positive electrode 121, the negative electrode 123, the separator 122, and the electrolytic solution, the coin-type battery 10 was produced in a glove box having an Ar atmosphere with a dew point controlled at −80 ° C.

For the negative electrode 123, a graphite powder having an average particle size of about 20 μm punched into a disk shape having a diameter of 14 mm and a negative electrode sheet coated with polyvinylidene fluoride on a copper foil were used. Further, as the separator 122, a polyethylene porous membrane having a film thickness of 25 μm was used. As the electrolytic solution, an equal amount mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using _{1M LiClO 4 as a supporting electrolyte (manufactured by Tomiyama Pure Chemical Industries, Ltd.) was used.}

[Battery evaluation]
The initial discharge capacity for evaluating the performance of the obtained coin-type battery 10 was defined as follows.

The initial discharge capacity is set to 0.05 C (270 mA / g as 1 C) for the current density with respect to the positive electrode after the open circuit voltage OCV (open circuit voltage) is stabilized by leaving the coin-type battery 10 for about 24 hours after being manufactured. ) Was charged to a cutoff voltage of 4.65 V, and after a one-hour rest, the capacity when the cutoff voltage was discharged to 2.35 V was defined as the initial discharge capacity.

When a battery evaluation was performed on a coin-type battery having a positive electrode formed by using the positive electrode active material, the initial discharge capacity was 282 mAh / g. Further, in order to evaluate the high discharge rate characteristics, the charge / discharge capacity is measured at 0.01C, then the charge / discharge capacity is measured 3 times at 0.2C, 0.5C, and 1.0C, and then 3 at 2.0C. The average value measured once was taken as the discharge capacity of the high discharge rate. The value was 216 mAh / g.

Table 1 summarizes the manufacturing conditions of this example, Table 2 shows the characteristics of the precursor obtained in this example, the characteristics of the positive electrode active material, and the coin-type battery manufactured using this positive electrode active material. Each evaluation is shown in Table 3. In addition, the same contents of Example 2 and Comparative Examples 1 and 2 below are shown in the same table.
[Example 2]
A precursor, a positive electrode active material, and a secondary battery were prepared and evaluated in the same manner as in Example 1 except that the time of the particle growth step was changed to 196 minutes. The results are shown in Tables 1 to 3.

The composition of the obtained positive electrode active material is represented as _{Li 1.5} Ni _0.154 Co _0.167 Mn _0.679 O _2.

In this example, it was confirmed that the average particle size of the particles contained in the precursor and the positive electrode active material was increased by lengthening the time of the particle growth step. However, it was confirmed that the battery characteristics were the same as those in Example 1.
[Example 3]
In order to add molybdenum as an additive element in the nucleation step and the particle growth step, an ammonium molybdate solution was added to the metal-containing mixed aqueous solution.

In addition, molybdenum is added to the metal-containing mixed aqueous solution so that the ratio of Mo to the total of Mo and Ni, Co, and Mn, which are other transition metal elements, is 1.5 at%. Ammonium acid acid was added and mixed. Further, the ratio of other metals, that is, Ni, Co, and Mn in the metal-containing mixed aqueous solution is the same as in the case of Example 2.

A precursor, a positive electrode active material, and a secondary battery were prepared and evaluated in the same manner as in Example 2 except that the above metal-containing mixed aqueous solution was used. The results are shown in Tables 1 to 3.

The composition of the obtained positive electrode active material is represented as _{Li 1.5} Ni _0.146 Co _0.167 Mn _0.673 Mo _0.015 O _2.
[Example 4]
In order to add molybdenum as an additive element in the nucleation step and the particle growth step, an ammonium molybdate solution was added to the metal-containing mixed aqueous solution.

In addition, molybdenum is added to the metal-containing mixed aqueous solution so that the ratio of Mo to the total of Mo and Ni, Co, and Mn, which are other transition metal elements, is 3.6 at%. Ammonium acid acid was added and mixed. Further, the ratio of other metals, that is, Ni, Co, and Mn in the metal-containing mixed aqueous solution is the same as in the case of Example 2.

A precursor, a positive electrode active material, and a secondary battery were prepared and evaluated in the same manner as in Example 2 except that the above metal-containing mixed aqueous solution was used. The results are shown in Tables 1 to 3.

The composition of the obtained positive electrode active material is represented as _{Li 1.5} Ni _0.160 Co _0.175 Mn _0.629 Mo _0.036 O _2.
[Example 5]
A precursor, a positive electrode active material, and a secondary battery were produced and evaluated in the same manner as in Example 2 except that the firing temperature in the firing step was changed to 950 ° C. when producing the positive electrode active material. The results are shown in Tables 1 to 3.

The composition of the obtained positive electrode active material is represented as _{Li 1.5} Ni _0.154 Co _0.167 Mn _0.679 O _2.

In this embodiment, when the positive electrode active material is produced, the specific surface area of the positive electrode active material obtained by raising the firing temperature in the firing step is 1.5 m ² / g or more and 8.0 m ² / g or less. It was confirmed that the specific surface area suitable for producing a mixture can be obtained. However, even in this case, it was confirmed that the initial discharge capacity and the discharge capacity under high discharge rate conditions can be increased.
[Example 6]
A precursor, a positive electrode active material, and a secondary battery were prepared and evaluated in the same manner as in Example 2 except that the firing temperature in the firing step was changed to 900 ° C. when producing the positive electrode active material. The results are shown in Tables 1 to 3.

The composition of the obtained positive electrode active material is represented as _{Li 1.5} Ni _0.154 Co _0.167 Mn _0.679 O _2.

In this embodiment, when the positive electrode active material is produced, the specific surface area of the positive electrode active material obtained by raising the firing temperature in the firing step is 1.5 m ² / g or more and 8.0 m ² / g or less. It was confirmed that the specific surface area suitable for producing a mixture can be obtained. However, even in this case, it was confirmed that the initial discharge capacity and the discharge capacity under high discharge rate conditions can be increased.
[Comparative Example 1]
The precursor, positive electrode active material, and secondary were the same as in Example 1 except that air was not blown into the reaction vessel during the production of the precursor and the time of the particle growth step was changed to 110 minutes. Batteries were manufactured and evaluated. The results are shown in Tables 1 to 3.

As described above, since air was not blown into the reaction vessel during the production of the precursor, the inside of the reaction vessel becomes an atmosphere of carbon dioxide gas and ammonia gas generated from the mixed aqueous solution during the production of the precursor, and is not an oxygen-containing atmosphere.
[Comparative Example 2]
A precursor, a positive electrode active material, and a secondary battery were prepared and evaluated in the same manner as in Example 2 except that the gas blown into the reaction vessel during the production of the precursor was changed to nitrogen gas. .. The results are shown in Tables 1 to 3.

The cross-sectional SEM observation of the obtained positive electrode active material was carried out in the same manner as in Example 1.

5A and 5B show cross-sectional images of typical particles. Note that FIG. 5A shows an overall view, and FIG. 5B shows an enlarged view of the particles surrounded by the broken line in FIG. 5A.

As a result of observing 100 or more particles, the proportion of particles having pores up to the center (porous particles) was 31%, and the porosity of the secondary particles was 18%. Further, it was confirmed that the porosity of the secondary particles that were not porous was 3% or less.

From the results in Table 2, it was confirmed that the precursors of Examples 1 to 6 all had the target composition. Further, it was confirmed that the positive electrode active material obtained from the precursor had a porosity of 10% or more of the porous particles and a ratio of the number of the porous particles of 100%.

It was confirmed that the initial discharge capacity and the discharge capacity under high discharge rate conditions can be sufficiently increased by using the battery using the positive electrode active material.

On the other hand, in Comparative Examples 1 and 2, it was confirmed that the H / Me of the precursor was less than 1.6, and the precursor having the target composition was not obtained. Therefore, it was confirmed that when the positive electrode active material was produced using the precursor, almost no porous particles were obtained, and the porosity of the porous particles was also reduced.

Then, it was confirmed that in the secondary battery manufactured using the positive electrode active material, both the initial discharge capacity and the discharge capacity under the high discharge rate condition are inferior to those of Examples 1 to 6. ..

The above is a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, a positive electrode active material for a non-aqueous electrolyte secondary battery, a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, and a positive electrode for a non-aqueous electrolyte secondary battery. Although the method for producing the active material has been described in the embodiments and examples, the present invention is not limited to the above embodiments and examples. Various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

This application is based on Japanese Patent Application No. 2016-0013666 filed with the Japan Patent Office on January 6, 2016, and Japanese Patent Application No. 2016-186242 filed with the Japan Patent Office on September 23, 2016. It claims priority, and the entire contents of Japanese Patent Application No. 2016-0013666 and Japanese Patent Application No. 2016-186242 are incorporated in this international application.

Claims (14)

Formula _{Ni x Co y Mn z M t} CO 3 ( where, in the formula, x + y + z + t = 1,0.05 ≦ x ≦ 0.3,0.1 ≦ y ≦ 0.4,0.55 ≦ z ≦ 0 8.8, 0 ≦ t ≦ 0.1 is satisfied, and M is one or more kinds of additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W). Represented nickel-cobalt-manganese carbonate complex and
It contains a functional group containing hydrogen and
A positive electrode active material precursor for a non-aqueous electrolyte secondary battery in which H / Me, which is the material amount ratio of the contained hydrogen and the contained metal component Me, is 1.60 or more. The additive element M in the general formula of the nickel cobalt manganese carbonate composite contains Mo and contains Mo.
The positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 1, wherein the content ratio of Mo in the metal component in the nickel cobalt manganese carbonate composite is 0.5 at% or more and 5 at% or less. A positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium metal composite oxide.
The lithium metal composite oxide is represented by the general formula _{Li 1 + α Ni x Co y} Mn z M t O 2 (0.25 ≦ α ≦ 0.55, x + y + z + t = 1,0.05 ≦ x ≦ 0.3,0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, M is an additive element, and Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Represented by one or more elements selected from W)
Containing porous secondary particles in which multiple primary particles are aggregated,
A positive electrode active material for a non-aqueous electrolyte secondary battery in which the porosity inside the secondary particles is 10% or more and 30% or less, and the number ratio of the secondary particles is 80% or more. The additive element M in the general formula of the lithium metal composite oxide contains Mo and contains Mo.
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 3, wherein the content ratio of molybdenum among Ni, Co, Mn, and the additive element M in the lithium metal composite oxide is 0.5 at% or more and 5 at% or less. Active material. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 3 or 4, wherein the specific surface area is 1.5 m ^{2 / g or more.} The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 3 to 5, wherein the tap density is 1.7 g / cc or more. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 3 to 6, wherein the discharge capacity under the high discharge rate condition (2C) is 195 mAh / g or more. Formula _{Ni x Co y Mn z M t} CO 3 ( where, in the formula, x + y + z + t = 1,0.05 ≦ x ≦ 0.3,0.1 ≦ y ≦ 0.4,0.55 ≦ z ≦ 0 8.8, 0 ≦ t ≦ 0.1 is satisfied, and M is one or more kinds of additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W). A method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, which comprises a nickel-cobalt-manganese carbonate composite represented by the above and a functional group containing hydrogen.
An initial aqueous solution containing an alkaline substance and / or an ammonium ion feeder in the presence of carbonate ions, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component. And a nucleation generation step to generate nuclei in a mixed aqueous solution
It has a particle growth step of growing nuclei formed in the nucleation step,
The nucleation step is a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, which is carried out in an oxygen-containing atmosphere by controlling the pH value of the mixed aqueous solution to 7.5 or less based on a reaction temperature of 40 ° C. .. The ammonium ion feeder is one or more selected from an aqueous ammonium carbonate solution, an aqueous ammonia solution, an aqueous ammonium chloride solution, and an aqueous ammonium sulfate solution.
The positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 8, wherein the alkaline substance is one or more selected from sodium carbonate, sodium hydrogen carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide. Production method. In the particle growth step, the mixed aqueous solution after the nucleation formation step contains an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions. Is a process of adding and mixing with
The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 8 or 9, wherein the ammonium ion concentration in the mixed aqueous solution is 0 g / L or more and 20 g / L or less during the particle growth step. .. The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to any one of claims 8 to 10, wherein the temperature of the mixed aqueous solution is maintained at 30 ° C. or higher in the nucleation step. The non-aqueous electrolyte 2 according to any one of claims 8 to 11, further comprising a coating step of coating the positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained in the particle growth step with the additive element. A method for producing a positive electrode active material precursor for a secondary battery. The coating step is
An aqueous solution containing the additive element is added to the slurry in which the positive electrode active material precursor for the non-aqueous electrolyte secondary battery is suspended, and the additive element is added to the surface of the positive electrode active material precursor for the non-aqueous electrolyte secondary battery. Step of precipitating,
The step of spray-drying the slurry in which the positive electrode active material precursor for the non-aqueous electrolyte secondary battery and the compound containing the additive element are suspended, and the positive electrode active material precursor for the non-aqueous electrolyte secondary battery, and the above. The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 12, which is one of the steps selected from the step of mixing a compound containing an additive element by a solid phase method. The positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained by the method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to any one of claims 8 to 13 is 60 ° C. or higher. A heat treatment process that heats at a temperature below ° C and
A mixing step of adding and mixing a lithium compound to the particles obtained by the heat treatment step to form a lithium mixture.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which comprises a firing step of firing the lithium mixture at a temperature of 600 ° C. or higher and 1000 ° C. or lower in an oxidizing atmosphere.